This invention is directed to semiconductors and, more particularly, monolithic semiconductors and electrical apparatus using such semiconductors.
In the past, most semiconductor dies have required good thermal coupling between the die and the surrounding environment in order to keep the temperature of the dies from rising to an undesirably high level. In many cases, the thermal coupling extends to a heat sink adapted to dissipate heat to the surrounding environment. In some cases the requirement for good thermal coupling must be traded off against an opposing requirement for good electrical isolation. That is, in many cases, good thermal coupling and good electrical isolation are mutually exclusive requirements. Thus, improved electrical isolation can only be obtained by reducing the thermal coupling requirement. Usually, in these cases, the trade off results in moderate thermal coupling being obtained, even though it may prove to be inadequate under some circumstances. In any event, most prior art semiconductor die have the best thermal coupling available considering the various trade offs that must be made. Conversely stated prior art semiconductor die have poor thermal isolation. The present invention is directed to semiconductor die that have a diametrically opposed thermal requirement. That is, the present invention is directed to semiconductor die that have good thermal isolation, rather than poor thermal isolation. Or, conversely stated, semiconductor die having poor thermal coupling to the surrounding environment.
In the past, when good thermal isolation was a requirement of a circuit or system, the usual solution has been to form a hybrid circuit using techniques designed to thermally isolate a silicon chip or die from the external ambient environment. Because discrete elements are involved, this approach has necessitated the use of relatively large geometry supporting and attachment structures. The inclusion of such structures tends to defeat the good thermal isolation requirement because such structures inherently produce larger than desired heat flows between the isolated portion of the overall circuit or system and the external environment. Moreover, the thermal capacity of such structures is usually higher than desired, also because of the relatively large geometries of the elements used to form the structures. Further, because discrete elements are attached together, it is extremely difficult to reliably and inexpensively yield pairs of matched devices, when matched devices are required. As a result, circuits using such devices have, in the past, not been as accurate as desired. Or, if accurate to an adequate degree, have been more expensive than desirable.
Therefore, it is an object of this invention to provide new and improved thermally isolated electrical devices and processes for making such devices.
It is also an object of this invention to provide thermally isolated electrical devices that include matched elements and processes for making such devices.
It is a further object of this invention to provide thermally isolated semiconductor dies and processes for making such dies.
It is another object of this invention to provide thermally isolated monolithic semiconductor dies and processes for making such dies.
It is still further object of this invention to provide thermally isolated monolithic semiconductor dies having matched regions and processes for making such dies.
It is still another object of this invention to provide new and improved semiconductor circuits including thermally isolated monolithic semiconductor dies.